JP2000156210A - Gasket for battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gasket having high accuracy, to improve its workability in processing it, and also adapt it for high volume production by forming it from a molding of a high-polymer film and by integrating the high-polymer film with a metal case of a positive electrode. SOLUTION: When this gasket is manufactured, firstly, a layered product composed by laminating a high-polymer film and metal foil each formed into an annular shape by drilling a hole in the central part is cut down into the same concentric shape as and larger than the hole and thereafter molded. Thereby, or by forming it into the same concentric outline as and larger than the hole, then molding it and thereafter cutting down along the outline, the gasket integrated with a metal case of a positive electrode can be manufactured. In this case, a crystalline high-polymer having a melting point of 150 deg.C or above, or an amorphous high-polymer having a glass transition temperature of 150 deg.C or above is used for the high-polymer film used as the gasket material, for instance, polypropylene or polyphenylene sulfide is particularly preferable in view of electrolyte resistance (chemical resistance) and a hygroscopic characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-sized, preferably used in a field where ultra-miniaturization, thinning, and weight reduction are required.
The present invention relates to a gasket for a thin lithium battery or the like, and a method for manufacturing a gasket for a battery capable of continuously and accurately manufacturing a gasket with good workability in insertion into a battery.

[0002]

2. Description of the Related Art Recently, due to demands for small size, light weight, and long life of functions in cameras, personal computers, mobile phones, and the like,
The demand for small and thin lithium batteries is increasing rapidly. Further, multi-functionality is required in card fields such as IC cards and ID cards.
Demands for thinner and lighter weight are becoming more stringent. To meet these requirements, the gasket, which is indispensable to the battery, is made thinner, as well as heat-resistant, chemical-resistant (electrolyte-resistant), heat-crack-resistant, etc. Needs to be satisfied. further,
A continuous processing method that is accurate and suitable for mass production is required.

Conventional lithium batteries which have been applied to the above-mentioned fields include primary and secondary batteries. In particular, secondary batteries are disclosed in, for example, JP-A-6-96869 and JP-A-6-96969.
Japanese Patent Application Laid-Open No. 111822 and the like are known. As a gasket used in the battery, a polypropylene film (hereinafter, sometimes abbreviated as a PP film), which is formed by cutting a hole in the center of a single body, or an O-ring such as rubber is generally used. It had been.

However, when a conventional film single piece is punched in a ring shape or an O-ring made of rubber or the like is used for a gasket, an ultra-thin battery (for example, a battery having a thickness of 0.5
(Approximately 1.0 mm), the workability and accuracy during the processing of the gasket deteriorate, and it becomes difficult to handle mass production. In addition, there was concern about the confidentiality of the contents of the battery (chemicals and electrolytes used for the positive electrode and the negative electrode).

[0005] PP film is widely used in this field, but it is a gasket formed by punching in the above-mentioned ring shape to improve the secrecy of the battery contents and the workability of the battery, and a gasket laminated with a metal foil. Is not found.

There is an example in which a polyphenylene sulfide film is punched in a ring shape and used as a gasket for a battery, but there is no molded product of the film used as a gasket for a battery.

A laminate of a polyphenylene sulfide film (hereinafter, sometimes abbreviated as a PPS film) and a metal foil and examples of known documents similar thereto are known as follows. There is no description that a laminated film with a metal foil was used. (1)
A flexible printed wiring board obtained by laminating a metal foil such as a copper foil and a PPS film (Japanese Patent Publication No. Sho 61-53880). (2) A metal-based circuit board in which a metal plate is laminated on one side of a circuit board using a PPS film as an insulating material (JP-A-1-9595)
586 publication). (3) A laminate in which a biaxially stretched PPS film / unstretched PPS film / metal plate is heat-sealed in this order (Japanese Patent Laid-Open No.
-90349).

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide a battery gasket and a high-precision battery gasket suitable for mass production which are highly accurate and excellent in workability in processing in order to cope with the thin and small battery. An object of the present invention is to provide a method for manufacturing a gasket for a battery which is excellent in secrecy and can be continuously produced.

[0009]

Means for Solving the Problems In order to solve the above problems, a gasket for a battery according to the present invention is a gasket used for insulating a positive electrode and a negative electrode constituting a battery, wherein the gasket is formed from a molded polymer film. Characterized by the following.

The gasket is preferably one in which a polymer film and a metal case of a positive electrode are integrated.

Further, a method of manufacturing a gasket for a battery according to the present invention includes the steps of:
By laminating a polymer film and a metal foil formed in a circular shape at the center by laminating a polymer film and a hole larger than the hole and concentrically, by cutting and shaping the same shape,
Alternatively, the method is characterized in that a gasket that is integral with the metal case of the positive electrode is manufactured by forming a shape larger than the hole, concentrically and in the same shape, and then cutting along the shape.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with preferred embodiments. The typical structure of the battery in the present invention comprises a positive electrode mixture, a negative electrode, an electrolytic solution, a separator, a gasket, and a positive electrode case, and a small lithium battery such as a button battery or a coin battery is particularly preferable. Also, primary batteries and secondary batteries are not limited. Taking a lithium battery as an example, as the positive electrode mixture, for example, a carbon-based compound such as carbon or fluorinated graphite, or a lithium composite oxide (for example, LiCoO ₂ ) can be used.

The negative electrode is generally made of sheet material such as lithium metal or lithium-aluminum alloy.
A substance capable of doping and undoping lithium ions is used.

The electrolyte may be any solution in which an electrolyte is dissolved in an organic solvent. As the organic solvent, a single substance or a mixture of propylene carbonate, ethylene carbonate, γ-butyl lactone, diethoxyethane, and the like can be used. As the electrolyte, lithium perchlorate, lithium borofluoride, lithium halide, or the like can be used.

The separator separates the positive electrode and the negative electrode, and a polypropylene thin film is most commonly used.

The gasket is used for the purpose of electrical insulation between the positive electrode and the negative electrode and prevention of leakage of the electrolyte. The shape of the gasket is square, circular or the like, and is generally formed by hollowing out the center and bending the outer end.

The positive electrode case is made of stainless steel (hereinafter, referred to as a stainless steel).
SUS), iron, aluminum, alloys of various metals, and the like are used, and serve as a case for housing the positive electrode material and a positive electrode terminal.

The first gasket of the present invention is formed by molding a conventional ring-shaped gasket so as to easily fit into the positive electrode case. That is, the gasket is formed by punching out the central part of the gasket to the size of the positive electrode part and forming it along the inner diameter of the square or cylindrical positive electrode case. The thickness of the gasket is in the range of 15 to 500 μm. It is preferable in terms of mechanical strength and insulating properties. Further, the outer diameter portion of the gasket may protrude or retract with respect to the outer diameter edge portion of the positive electrode metal case.

The form of the second gasket of the present invention is improved in accuracy and workability (workability during processing) by reducing the size and thickness.
In order to improve the above, the first gasket is integrated with the positive electrode metal case in a form laminated on the inside of the positive electrode metal case. Here, "integration" means that the gasket and the positive electrode case can be handled as one component. Whereas the conventional gasket and the case are separately manufactured and inserted when assembling the battery, the second form of the gasket of the present invention does not require an insertion step into the battery. This point is an important requirement for achieving the object of the present invention, and the gasket of the second embodiment is particularly preferable. Further, the outer diameter portion of the gasket may protrude or retract with respect to the outer diameter edge portion of the positive electrode metal case.

The film of the present invention has a thickness of 10 to 500.
μm is preferable, and 20 to 20 μm is preferable from the standpoint of electric insulation reliability and thickness reduction.
A thickness of 350 μm is particularly preferred. The thickness of the metal foil of the case is preferably from 10 to 300 μm in terms of strength, workability, and weight reduction.

The term “battery” used in the present invention includes both non-chargeable and non-chargeable primary batteries and rechargeable and rechargeable secondary batteries. The size of the battery has an outer diameter of 8 to 30 mm and a height of 0.2 to 5 mm. It is particularly preferable in terms of the effects of the present invention.

The polymer film used for the gasket material of the present invention is a crystalline polymer having a melting point of 150 ° C. or higher,
The amorphous polymer preferably has a glass transition temperature of 150 ° C. or higher, and examples thereof include polymer films of polyester, polypropylene, polyphenylene sulfide, polyimide, polyetherimide, polycarbonate and the like. The film may be a stretched film or an unstretched film. Particularly preferred are polypropylene (hereinafter may be abbreviated as PP) and polyphenylene sulfide (hereinafter may be abbreviated as PPS) from the viewpoints of resistance to electrolytes (chemical resistance), moisture absorption, and stress cracking. .

The PP film of the present invention refers to a propylene polymer, and one having a melting point of 150 ° C. is preferred in terms of heat resistance. The film refers to an unstretched film formed by melt extrusion molding and a film obtained by biaxially stretching and heat-treating the unstretched film. Even if additives such as a colorant, a lubricant, an antistatic agent, and other kinds of polymers are appropriately added to the film, there is no problem as long as the object of the present invention is not hindered. further,
Various discharge treatments or top coat treatments may be performed on the film surface for the purpose of easy adhesion or the like. Further, two or more layers of PP films may be joined via an adhesive or may be heat-sealed.

The thickness of the PP film is 10 to 50.
The range of 0 μm (particularly preferably 20 to 350 μm) is preferable from the viewpoint of insulation reliability and moldability of the gasket.

The PPS film of the present invention refers to a film obtained by melt-molding a PPS resin composition containing polyphenylene sulfide as a main component. It is preferable in terms of characteristics and the like. The PPS of the present invention is 85 mol% of the repeating unit.
The above (preferably 90 mol% or more) refers to a polymer composed of structural units represented by the following structural formula (Formula 1). If the content of such a component is less than 85 mol%, the crystallinity, softening point, etc. of the polymer may be reduced, and the heat resistance, mechanical properties, chemical resistance, etc., which are the characteristics of PPS, may be impaired.

[0026]

Embedded image

In the above PPS, the repeating unit 15
If the amount is less than mol%, preferably less than 10 mol%, a unit containing a copolymerizable sulfide bond may be contained. The method of copolymerizing the polymer may be random or block type.

The resin composition containing PPS as a main component means that 70% by weight or more is a PPS polymer. If it is less than 70% by weight, heat resistance, chemical resistance and mechanical properties may be reduced. If it is less than 30% by weight, a resin other than PPS, a lubricant, an antistatic agent, a coloring agent, and the like may be added.

The relative crystallinity of the PPS film of the present invention measured by wide-angle X-ray is in the range of 6 to 30 (more preferably 7 to 25) in terms of thermal dimensional stability and formability (bending and punching). Particularly preferred. When the relative crystallinity is less than 6, heat shrinkage tends to be caused by lamination with a metal foil, and it is difficult to produce a gasket with high accuracy. On the other hand, if the crystallinity exceeds 30, the mechanical properties are lowered, and the glass tends to be cracked or torn by bending or punching.

The thickness of the PPS film of the present invention is 10
The thickness is preferably from 500 to 500 µm (more preferably in the range from 20 to 350 µm) from the viewpoint of insulation and workability.

The metal foil of the present invention is not particularly limited, but may be SU
S foil is particularly preferred in terms of workability and corrosion resistance. The thickness is preferably in the range of 10 to 300 μm from the viewpoint of workability.

The gasket used in the battery of the present invention is a gasket obtained by laminating the above-mentioned polymer film and metal foil via heat sealing or via an adhesive into a desired shape and size, and integrally forming a positive electrode case. It is.

[0033] Due to the integral molding, a highly accurate gasket can be formed without displacement when assembled into a battery. In addition, it can be applied to an ultra-thin battery with high accuracy. Furthermore, it can be processed continuously and is suitable for mass production.

At this time, the thickness ratio A / B of the polymer film thickness (A) to the metal foil thickness (B) is in the range of 0.3 to 5.0 (more preferably, 0.35 to 4.0). 5) is preferable in view of the characteristics and workability of the gasket. If the A / B is less than 0.3, the force applied during the molding process is increased, and the polymer film may be broken or damaged, resulting in a lack of insulation reliability. Conversely, if it exceeds 5.0, the reinforcing effect of the metal foil is small, and if the operating temperature of the battery increases, the case may be deformed due to a change in the dimensions of the film.

A preferred method of manufacturing the gasket for a battery according to the present invention will be described. However, it can also be manufactured by other methods. First, the polymer film of the present invention is
An example in which an S film is used will be described.

The PPS of the present invention can be obtained by reacting alkali sulfide and paradihalobenzene in a polar solvent at an elevated temperature. In particular, it is preferable to react sodium sulfide with paradichlorobenzene in an amide-based high-boiling solvent such as N-methyl-pyrrolidone (hereinafter sometimes abbreviated as NMP). Caustic, to adjust the degree of polymerization,
Add a polymerization aid such as an alkali metal carboxylate,
The reaction is preferably carried out at a temperature of from 230 to 280C. The pressure and the polymerization time in the polymerization system are appropriately determined depending on the desired degree of polymerization, the type and amount of the auxiliary agent used, and the like.

A lubricant and the like are added to the obtained PPS, blended by a Henschel mixer or the like, and supplied to an extruder (preferably an extruder having one or more vent holes) to supply 290 to 3
Melt and kneaded at a temperature of 60 ° C and extruded from a suitable die
Obtain a PS resin composition.

The composition is supplied to a melt extruder, melted at a temperature equal to or higher than the melting point of the resin composition (preferably 290 to 360 ° C.), and extruded from a slit die and cast on a rotating metal drum. And quenching to obtain an unstretched, non-oriented film. Heat treatment may be performed if necessary, but it is preferable to control the relative crystallinity of the film to 6 to 30 by appropriately controlling the temperature and time of the heat treatment.

To obtain a biaxially stretched film, a method such as a sequential biaxial stretching method using a roll group and a tenter or a simultaneous biaxial stretching method can be used for the unstretched film obtained above.
The stretching condition is a temperature of 85 to 105 ° C. and a length and width of 1.5 to 1.5 ° C.
It is preferable to carry out at a magnification in the range of 4.5 times. The film thus obtained is heat-treated under a limit of 15% or less. The conditions of the heat treatment are preferably in the range of 220 to -5 ° C. for controlling the crystallinity of the film to 6 to 30%. If the conditions are lower than 220 ° C., the crystallinity of the film cannot be increased to 6 or more, and the heat shrinkage tends to increase. Conversely, if the melting point exceeds -5 ° C. or exceeds the melting point, the crystallinity exceeds 30. The mechanical properties of the film are reduced, and it is difficult to achieve the object of the present invention. If the stretching ratio is low and the heat treatment temperature is higher than the melting point of −5 ° C., the tendency is undesirably increased.

In the gasket formed by molding the film of the present invention, the above-mentioned film is formed in an annular shape. A hole is formed in the desired inner diameter of the gasket so as to fit the inner diameter wall of a square or cylindrical positive electrode case. It can be obtained by molding into a corner or a cylinder and cutting the corner or the cylinder in the height direction to the required size. Here, the term “annular” refers to a corner or a circle, and a hole may be punched in a film or a molded product may be cut using a cutting tool or a punching method represented by a punch or a Thomson blade. In addition, a known molding method such as vacuum, compression, and press can be used for molding.
The temperature during molding may be either normal temperature or a heating atmosphere, but when a PPS film is used, heat molding at 90 ° C. to 220 ° C. is preferable from the viewpoint of moldability.

Next, a preferred embodiment of the present invention will be described with reference to an example of a method for manufacturing an integrated gasket of a positive electrode metal case and a PPS film.

First, in the method of laminating with a metal foil via an adhesive, an adhesive is applied to a film, and a hole is formed in an annular shape (a desired inner diameter of a gasket). The ring may be square or circular, but is generally circular. The hole may be formed by cutting with a blade into a desired shape, or by using a press punching method represented by a Thomson blade. As the adhesive, a well-known curable adhesive such as an epoxy-based, silicone-based, or urethane-based adhesive, a thermoplastic adhesive, or an adhesive can be used. An adhesive is applied to one surface of the PPS film by a known method such as a glass rod, a gravure coating method, a reverse coating method, etc., and dried if necessary. Next, it is laminated on one side of the metal foil. The lamination method is lamination between a plate-shaped press and a press roll. The obtained laminate is cured with heat, ultraviolet light, or the like, if necessary. Adhesive thickness is 20μm
The following are preferable in terms of workability of forming and punching, heat resistance, and electric characteristics. In the case of laminating with a metal foil by heat fusion without using an adhesive, the film is punched into a desired annular size and thermocompression-bonded at a temperature near the melting point of the film (or higher than the glass transition temperature for an amorphous film). I do. The method of lamination can be a hot plate press method, a roll press method, or the like, but prior to the above-mentioned adhesive application and heat fusion, a corona discharge treatment, a plasma treatment, and a purpose of easy adhesion such as a primer treatment. It is preferable to perform the surface treatment singly or in combination from the viewpoint of improving the adhesion to the metal. In the laminate of the film and the metal foil, the film or the metal foil may be cut in advance to a desired outer diameter.

The laminate with the metal foil thus obtained is punched out at a desired size that is larger than the hole size of the previously opened annular portion, concentric and of the same shape. The thus obtained product is formed into a square or cylindrical shape (positive case) with the film surface inside, to produce a gasket integrated with the metal case. Alternatively, the outer surface may be punched after the film surface is formed into a concentric, same shape inside the polymer film having a size larger than the size of the hole in the ring-shaped polymer film. The punching method may be cutting with a blade or pressing with a Thomson blade or a punch. The molding method is vacuum, press,
A method such as compression can be used. The molding may be performed at room temperature or in a hot atmosphere.

The gasket of the present invention thus obtained is
Since the steps from lamination of the film and the metal foil to punching and molding can be performed in one step, the gasket has no variation and the precision is high, and the workability is good, so that it can be easily applied to an ultra-thin lithium battery. In addition, since continuous products of films and metal foils can be continuously processed, it is suitable for mass production.

[Method for Evaluating Characteristics] Next, the method for evaluating characteristics and the criteria for evaluation used in the description of the present invention will be described. (1) Thermal shrinkage rate Measured according to JIS C2151 at a temperature of 150 ° C.
The display was made with the larger numerical value in the longitudinal direction and the width direction.

(2) Deformability of Case The warpage of the end of the integrated gasket and positive electrode case was confirmed with a microscope (10 times) and evaluated according to the following criteria. ：: No warpage. Δ: Although slightly warped, there is no practical problem. X: A level with a large warpage and a problem in function.

(3) Scratches in Gasket The scratches in the film portion of the gasket and the positive electrode case integrated product were observed with a microscope and evaluated according to the following criteria. ：: No hindrance is found. Δ: Deformation part of the film has some scratches, but has no problem in functions such as insulation. ×: Defects in the film are flawed or torn, and there is a problem with functions such as insulation from the depth of the flaws and the thickness of the film.

(4) Ratio of PPS Film Thickness to Metal Foil Thickness (A / B) After the gasket was prepared, its cross section was observed and measured with a microscope.

(5) Relative crystallinity of film From the diffraction profile of each sample at wide-angle X-ray,
0) The maximum intensity (I ₂₀₀ ) of the peak and the intensity (I ₂₅ ) at 2θ = 25 were measured as internal standard values, and the ratio between the two was defined as the relative crystallinity (I ₂₀₀ / I ₂₅ ).

(6) Formability After forming into a gasket, the surface of the film was observed with a microscope, and the crack state of the film was evaluated according to the following criteria. ：: No crack at all. Δ: Cracks are slightly generated X: Cracks are generated at a level that adversely affects insulation.

(7) Insertion test into battery A battery was prepared by the following method (the electrolytic solution was not used).
Then, it was determined according to the following evaluation criteria. Li, Ni as positive electrode agent
Using O ₂ , Al powder was mixed with a conductive agent (acetyl black powder) and a binder (polytetrafluoroethylene) and molded to a thickness of 0.5 mm and a diameter of 10 mm. The negative electrode used metallic lithium. Also, a SUS sealing plate was prepared. The separator used was PP made of micropores.

In a battery using the gasket of the present invention, metallic lithium was pressed against a sealing plate, a separator and a positive electrode agent were placed on the metallic lithium, and stored in a positive electrode case integrated with the gasket. A battery was made by crimping it moderately.

On the other hand, the gasket of the first embodiment of the present invention and the gasket manufactured by the conventional method are prepared by pressing metallic lithium on a sealing plate, inserting the gasket, and arranging a separator and a positive electrode agent on metallic lithium in this order. Then, the battery was housed in a positive electrode case, and the case was appropriately crimped to prepare a battery. ：: There is no displacement of the gasket at all, and there is no problem in workability. Δ: Displacement of the gasket or the like sometimes occurs, resulting in poor workability. ×: Position shift occurs, workability is poor, and considerable time is required for insertion.

(8) Melting point of film Measured by a DSC-2 type differential scanning calorimeter manufactured by PERKIN ELMER under an inert gas atmosphere under the following conditions. Sample weight: 5mg Heating rate: 10 ° C / min

(9) Heat resistance A battery was prepared by the method of the above (7), and was heated at a temperature of 100 ° C.
After aging for 00 hours, the gasket was taken out of the battery and evaluated according to the following criteria. ：: No discoloration, bent by hand, and has the same strength as the gasket before aging. Δ: Discoloration is slight, but not broken by hand bending. ×: Discoloration is severe, and the level breaks when bent by hand.

[0056]

The present invention will be described in detail with reference to the following examples. Example 1 (1) Preparation of PPS raw material As a PPS polymer, T1880 (32 manufactured by Toray Industries, Inc.) was used.
Using a powder having a melt flow of 0 ° C. and a melting point of 288 ° C.), 0.5% by weight of calcium carbonate particles having an average particle size of 1 μm were blended with a Henschel mixer. Further, the polymer was supplied to a twin-screw extruder having a hole diameter of 30 mm, extruded at a temperature of 320 ° C. from a circular die having a diameter of 2 mm and formed into a 3 mm length with a cutter after cooling with water.

(2) Production of PPS film The PPS raw material obtained in (1) was dried at a temperature of 180 ° C. for 3 hours, and further dried at a temperature of 150 ° C. for 5 hours.
Extruded at a temperature of 320 ° C. with an extruder having a hole diameter of 0 mm, formed into a sheet shape with a die having a width of 600 mm and a lip gap of 3 mm, and cast with a metal drum controlled at a temperature of 30 ° C. to obtain an unstretched PPS film having a thickness of 2000 μm. . The obtained unstretched sheet was stretched 3.9 times in the longitudinal direction and 3.5 times in the width direction by the successive biaxial stretching method. The stretching temperature is
The temperature was 99 ° C. in both the longitudinal direction and the width direction. Further, heat treatment was performed in a heat treatment zone following the tenter stretched in the width direction. The heat treatment temperature was 270 ° C. The relaxation rate in the width direction was 5%. The thickness of the obtained film was 100 μm. The relative crystallinity was 12.

(3) Preparation of Gasket for Battery One side of the film obtained above was subjected to a corona discharge treatment of 6000 J / m ² . Next, the following adhesive was provided on the surface-treated surface so as to have a thickness of 10 μm after curing. A gravure roll coater was used as a method of applying the adhesive. The drying of the adhesive was performed at a temperature of 120 ° C. for 1 minute. Adhesive: Adcoat 76P1 (Polyurethane-based adhesive) manufactured by Toyo Morton Co., Ltd. Main agent / curing agent = 100/2 Prepared adhesive concentration = 27% (solvent: ethyl acetate)

The film with the adhesive was punched out into a circle having a diameter of 12 mm by a punch, and
A film punched to a size of 2 mm was obtained. A 100 μm SUS foil is applied to the film at a temperature of 120 ° C. and a pressure of 1 kg.
The layers were laminated by a hot plate press under the condition of / cm ² and thermally cured at a temperature of 60 ° C. for 24 hours. The obtained laminate is a laminate with metal having no film in the center with a portion having a diameter of 12 mm.

The laminated body was prepared without the film and having a diameter of 12 m.
It was punched by a Thomson punching machine so as to have a diameter of 16 mm concentrically with a circle of m. Further, the film is aligned with a pressure molding machine, with the film surface inside and a height of 2 mm and a diameter of 1 mm.
It was formed into a 5.5 mm cylindrical shape. The gasket thus obtained was a positive electrode case integrated type having an outer diameter of 15.5 mm and a height of 2 mm (referred to as gasket-1).

Comparative Example 1 The PPS film obtained in Example 1 was punched into a donut type gasket having an inner diameter of 12 mm and an outer diameter of 16 mm. The method used for punching is a Thomson punching machine (Gasket-2). In the positive electrode case, the SUS foil used in Example 1 was punched into a circular shape having an outer diameter of 16 mm. Comparative Example 1
In this method, the gasket and the positive electrode case are separately formed (they are not integrated), and are separately incorporated when assembling the battery.

Example 2 An unstretched PP film having a thickness of 100 μm (Trefane NO. Manufactured by Toray Industries, Ltd., melting point: 163 ° C.) was used as a polymer film. One side of the film was subjected to a corona discharge treatment of 6000 J / m ² . Moreover, the method of Example 1 was used for the gasket manufacturing method (gasket-3).

Comparative Example 2 A gasket and a positive electrode case were prepared from the PP film used in Example 2 by the method of Comparative Example 1.
4).

Example 3 The same procedure as in Example 1 was carried out to form a cylindrical shape with the hole of the laminated film and the metal having a hole formed in the film in the same manner as in Example 1, and the outer diameter was adjusted. Was cut off to obtain a gasket (gasket-5) having the same dimensions as in Example 1.

(Evaluation) Examples 1 and 2, 3 and Comparative Example 1
Tables 1, 2 and 3 show the results of the evaluations of Examples 2 and 3.
Since the gaskets of the present invention of Examples 1 and 2 are integrated with the positive electrode case, there is no displacement of the gaskets, and the gaskets are accurate.
The battery was assembled with good workability. However, in Comparative Examples 1 and 2, since the gasket and the positive electrode case were separately prepared and assembled separately, the gasket was easily displaced during battery assembly, and the workability was considerably poor. Example 3
The stamping and shaping processes are the reverse of those of the first embodiment. However, a gasket having exactly the same characteristics as the first embodiment and good workability of insertion into a battery can be obtained.

Examples 4 to 6 According to the method of Example 1, the thickness was 45 μm, 75 μm, 125 μm.
m PPS films were prepared. Further, as the SUS foil, 150 μm, 50 μm, and 25 μm were prepared, and a gasket was prepared by the method of Example 1 using the following combinations. Gasket-6: PPS45 μm / SUS150 μm Gasket-7: PPS75 μm / SUS50 μm Gasket-8: PPS125 μm / SUS25 μm (Evaluation) Table 1 shows the evaluation results of the gaskets of Examples 4 to 6.
The results are shown in Tables 2 and 3. If the ratio of the thickness of the polymer film to the lamination thickness of the metal foil (A / B) is less than 0.3, the film may be scratched when it comes into contact with the positive mold and the molding die. Only electrical insulation tends to be a problem. Conversely, if the ratio exceeds 5, dimensional changes such as the thermal contraction coefficient and thermal expansion coefficient of the film substrate will exceed the rigidity of the metal foil,
The case is easily deformed. The lamination thickness ratio is 0.3 to
The range of 5 is particularly preferred in that the present invention is effectively exhibited.

Example 7 A PPS film was produced by the method of Example 1. At this time, the heat treatment was performed at 210 ° C. At this time, the relative crystallinity of the film was 5.6. The gasket was performed by the method of Example 1 (gasket-9).

Example 8 A PPS film was produced in the same manner as in Example 1. The heat treatment temperature at this time was 287 ° C. The relative crystallinity of the obtained film was 33. The gasket was prepared using the method of Example 1 (Gasket-10).

(Evaluation) Tables 1, 2, and 3 show the evaluation results of the three types of gaskets of Examples 1, 7 and 8. It is understood that the relative crystallinity of the PPS film in the present invention is particularly preferably in the range of 6 to 30. That is, the gasket-9 of Example 7 having a relative crystallinity of 5.6 was PPS.
Since the heat shrinkage of the film is large, when heat is applied to the integrally molded article in the positive electrode case, the case itself tends to be easily deformed. Conversely, when the relative crystallinity of the PPS film exceeds 30, as in Example 8, the PPS film becomes brittle, and cracks tend to occur during integral molding, and scratches tend to occur.

Example 9 An unstretched PP film (thickness: 100 μm) was obtained by a known method using an ethylene-propylene copolymer (ethylene content: 3 mol%) as a polypropylene polymer. The melting point of this film was 148 ° C. Using this film, a gasket was prepared by the method of Example 2 (gasket-
11).

(Evaluation) Tables 1, 2, and 3 show the evaluation results of Example 9 in comparison with the characteristics of the gasket of Example 2.
A gasket using a PP film has poor heat resistance because the melting point of the film is 150 ° C. or less, and tends to reduce the reliability of electric insulation and the maintenance of confidentiality of battery contents.

Example 10 Using the film of Example 1, a circular hole having a diameter of 12 mm was formed in the film. The film was formed into a cylindrical shape having an outer diameter of 15.3 mm and a height of 2 mm, which was concentric with the circular hole of the film. The molding method was press molding and the temperature was 200 ° C. The gasket (film-forming gasket) obtained by cutting to the outer diameter is referred to as Gasket-12.

(Evaluation) The evaluation results of the gasket of Example 11 are shown in Tables 1, 2 and 3. Example 10 is a first embodiment of the gasket of the present invention. Although the gasket according to the second embodiment of the present invention has a little difficulty in inserting into a battery, the positioning is simpler, the accuracy is higher, and the workability is better than the gaskets of Comparative Examples 1 and 2.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

The present invention has the above-mentioned structure, that is, the gasket serving as an insulating material is formed or the metal case of the positive electrode is integrated, so that the accuracy in assembling the battery and the workability are improved. The best gasket for thin batteries could be provided. Further, when the gasket and the positive electrode metal case are manufactured by integral molding, a gasket can be formed continuously and with high accuracy, and can be used for mass production.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Taiichi Kurome 1 at 900 Aji, Oji, Kobe-cho, Anpachi-gun, Gifu Prefecture Inside the Gifu Factory of Toray Industries, Inc. 1 F-term in Matsumoto Manufacturing Co., Ltd. (reference)

Claims (8)

[Claims] 1. A gasket for use in insulating a positive electrode and a negative electrode constituting a battery, wherein the gasket is formed of a molded polymer film. 2. The battery gasket according to claim 1, wherein the polymer film and the metal case of the positive electrode are integrated. 3. The gasket for a battery according to claim 1, wherein the polymer film is a polypropylene film. 4. A polypropylene film having a melting point of 150
The gasket for a battery according to claim 3, wherein the temperature is higher than or equal to ° C. 5. The gasket for a battery according to claim 1, wherein the polymer film is a polyphenylene sulfide film. 6. The gasket for a battery according to claim 5, wherein the relative crystallinity of the polyphenylene sulfide film is 6 to 30. 7. The gasket for a battery according to claim 1, wherein the battery is a small lithium battery. 8. A laminate formed by laminating a polymer film and a metal foil having a hole formed in the center thereof and having an annular shape, and cutting the laminate into a shape larger than the hole, concentrically and in the same shape, and then molding the laminate. The gasket integrated with the metal case of the positive electrode is manufactured by forming a shape larger than the hole, concentrically, and having the same shape, and then cutting off the shape. A method for producing the gasket for a battery according to the above.